Quantifying Methane Influx from Sewer into Wastewater Treatment Processes

Area of Science:

• Environmental Science
• Environmental Engineering
• Atmospheric Chemistry

Background:

• Wastewater treatment plants (WWTPs) are significant sources of methane (CH4) emissions.
• Current monitoring of CH4 emissions from WWTPs is challenging due to the
• black box
• nature of treatment processes.
• The contribution of sewer-derived CH4 influx to overall WWTP emissions remains poorly understood.

Purpose of the Study:

• To quantify CH4 emissions from WWTPs in China.
• To investigate the impact of sewer CH4 influx on WWTP emissions.
• To assess the potential of odor control systems for CH4 monitoring and mitigation.

Main Methods:

• Quantified CH4 emissions from six WWTPs across China.
• Utilized existing multizonal odor control systems for monitoring.
• Conducted 24-hour online monitoring at the Guiyang WWTP.
• Correlated CH4 fluctuations with water consumption and influent Chemical Oxygen Demand (COD).

Main Results:

• In Beijing WWTP, nearly 90% of CH4 emissions originated from sewer pipes, affecting aerobic treatment zones.
• Guiyang WWTP showed CH4 release at the inlet well, with fluctuations linked to water usage and COD.
• Monitored CH4 emission factors ranged from 1.5 to 13.4 gCH4/kgCODrem, exceeding previous studies.
• Odor control systems proved effective for CH4 tracing and monitoring.

Conclusions:

• Sewer CH4 influx is a critical factor in WWTP emissions, often underestimated.
• Odor control systems offer a viable and cost-effective method for CH4 management in WWTPs.
• Accurate CH4 emission assessment requires accounting for sewer influx.